1. Technical Field of the Invention
The present invention relates generally to a photosensitive polymer and a resist composition using the same. More particularly, the present invention relates to a photosensitive polymer including silicon and a resist composition including the same.
2. Discussion of Related Art
As semiconductor devices become more highly integrated, a photolithography process requires patterns with finer detail. In addition, the fabrication of semiconductor devices on a scale of one gigabit requires a new light source having a shorter wavelength, such as an ArF excimer laser (λ=193 nm) or a F2 (λ=157 nm) laser, than the conventional light source, such as a KrF excimer laser (λ=248 nm). Further, a new resist composition is required for the new light source.
However, the new resist composition created for use with the ArF or F2 has some problems, e.g., dry etch resistance or pattern collapse, as compared with a conventional resist composition used in conjunction with a KrF or i-line (λ=365 nm) in a conventional photolithography process. Thus, a new process and a new material for the resist composition are required to prevent the above identified problems.
Generally, there are two types of photolithography processes. One is a single-layer resist (SLR) process and another is a bi-layer resist (BLR) process. In the SLR process, a photoresist is patterned by using a photolithography process. Next, a desired layer is patterned by using the patterned photoresist. In the BLR process, a bottom layer and a top photoresist (TPR) are sequentially stacked. The TPR is patterned by a photolithography process. The bottom layer is then patterned by using the TPR pattern as a dry etch mask, thereby forming a bottom layer mask. Next, a desired layer is patterned by using the bottom layer mask. The BLR process provides no pattern collapse and greater dry etch resistance as compared to the SLR process. Thus, the BLR process is preferred for forming a very fine pattern. The BLR process usually employs TPR compositions containing a polymer in which a monomer containing a group with silicon is polymerized.
Foster discloses a photosensitive polymer for a TPR having the following formula in “Second Generation 193 nm Bilayer Resist”, Proc. SPIE. Vol. 3678, pp. 1034-1039. 
In the above formula, a third monomer contains a bulky group of Si—O—Si. Since Silicon (Si) has a high resistance with respect to a dry etch process, it is preferable to have a high concentration of Si. However, silicon is hydrophobic. Due to the bulky Si—O—Si group contained in the above formula, the hydrophobicity of the photosensitive polymer increases causing a decrease in adhesive strength or a decrease in wet-ability to a hydrophilic bottom layer. Thus, the photoresist polymer having a high concentration of Si has a low resolution and a decrease in performance.
Therefore, a need exists to provide a photosensitive polymer to be used as a top photoresist in a BLR process that has a greater dry etch resistance and adhesive strength than a conventional photosensitive polymer. In addition, there is also a need to provide a resist composition using the same.